Cam gods need some light on this

Ok so im looking for some help on a cam....Looking for a turbo grind trying to keep it in the 6000rpm range but looking at a roller due to the higher spring psi with the boost ect ect......

Block: Ford 460 D1VE A2A

Crank: 4.300

Rods: 6.800

Piston 8.8.1cr 536g

Heads: D3ve with a little clean up.... dont have any flow numbers so i will say stock flow numbers

Intake: m-9424-g429

Turbos: BG s400 with racecovers 15-20psi

Trans: 2 speed powerglide

Chassis: 25.5 3300lbs

Front & Rear Tire: MT front runner 26x4x15 MT ET Drag 29.5x10.5wx15

rear gear in the ball park of 3.5x

Well it dont have to be a roller if you think I dont need it.. Thank you Jason

One question Jason, if your making say 10 lbs of intake boost, how much pressure would there be in the exhaust before the turbo? I know it will be a ball park due to the wide range of variables. I never thought about valve spring pressure changing for boost, but it makes sense.

Bill

Ill have to do the math ill post it in the morn... On the wife blackberry so I'm still don't know how to work this thing that good.

Just shotting numbers a 2.25 vavle. At 10 psi boost you are lookig at 3sq in so that will be 30. Lbs on the back side of the vavle when closed the ehxs vavle don't see the same type of psi trying to open it it has to work harder to open with the greater cylinder psi so the exhs vavle can run the the same lbs spring just the intake spring has to have the heaver spring psi but the roller dose make it nice for the fast ramp speed I hope I make sence I ramble on so times boy this is one long sen....lol

No the exhaust valve sees MORE PSI than the intake in a turbo application by about 2:1. With that said because of it's smaller diameter the exhaust valve has much less area and therefore less force trying to hold it off the seat under boost conditions.

I can't imagine that it would require anything all that special to work well to 6000rpm. Late intake closure isn't generally harmful, opening the exhaust valve early can put more heat into the exhaust system and help to spool boost more quickly at the expense of much higher EGT's and possibly less HP. I'd say that overlap and cam advance are not your friend in this application. So a wide lobe sep and nearly straight up cam timing would probably be where I would try it first.

Doesnt the exha... vavle see more psi to open not trying to stay closed im not cam pro thats why im looking i guess you would us a little heaver spring on the exha.. Well been looking at a lot of small block stuff and i see a lot of them with a 114cl i for got to say that im looking in to E85 as fuel if that is needed.

Thanks Dave for the info this cam stuff is like talking a different lang....to me im lost maybe some one can have cam 101 with me so whats is this stuff BTDC , ABDC , BBDC , ATDC , Lobe-Center Angle , Intake Centerline: I have a ? would you faver the intake side on the lift and duration ?

Duration:

Duration is critical to a turbo setup since its probably the single most important event of a turbo motor (i.e. time valve sits open and closed). Since the air is being forced instead of drawn into and out of the combustion chamber, duration will be your largest variable on how that incoming/outgoing air is managed.
Duration when using a manifold or log design on most turbo cams is usually about 6 degrees more intake duration than exhaust duration (226/220, 240/234). This is mainly because a manifold/log design will typically see higher then a 2:1 pressure ratio in the exhaust ( as high as 4:1 with some logs). By using a reverse split duration this will somewhat help prevent from getting exhaust gas reversion.
Duration when using an efficient header setup with most turbo cams will usually be (230/230, 224/224) or better known as a dual pattern cam. The thinking is with the exhaust backpressure being only 2:1 you can leave the exhaust valve open a little longer then if the exhaust backpressure was 3:1 or higher. Also some of the new turbo designs produce a much lower backpressure with the advent of better flowing turbine wheels and housings which further decrease the total amount of backpressure created by the system.




Overlap:

Overlap definition, is the time period when both the exhaust valve and the intake valve are open at the same time. The exhaust valve needs to stay open after the piston passes TDC in order to use the vacuum created of the exiting exhaust gases to maximize the amount of exhaust gas drawn out of the cylinder. The intake valve opens before TDC in order to use the vacuum created by the exiting exhaust gases to start drawing the intake charge into the cylinder.


This sequence of events above are controlled by the duration and LS (Lobe separation) of the cam. On a typical N/A motor this is essential since you have no pressure being developed on the intake side to push the charge into the combustion chamber. The problem with this event is a turbocharged motor will create a larger amount of backpressure on the exhaust side. Due to this event the above definition will not apply. Reason being is, when the intake valve opens at BTDC, the burned gasses in the chamber will exit out the intake since the pressure is lower than the exhaust. Since this is true you would not want to open the intake valve until the piston has started going down, ATDC. This will lower the combustion chamber pressure till it's below the intake manifold pressure.


To calculate the overlap of your cam simply follow these steps below:
**Example turbo cam:**

Duration @ .006 218/212

Lift .544/.544 lift

Lobe Separation (LS) 114

Add the intake and exhaust durations
Divide the results by 4
Subtract the LSA
Multiply the results by 2

Overlap is -6.5 Degrees of overlap

**Example N/A cam :**

Duration 236/242

Lift .568/.576

Lobe Separation (LS) 112

Add the intake and exhaust durations
Divide the results by 4
Subtract the LSA
Multiply the results by 2

Overlap is 15 Degrees of overlap

Above was the process on how to calculate your cams overlap. As you can see, the overlap in the 2 cams differ greatly. Running the N/A cam example on a manifold setup would be a horribly in-efficient setup and the engine would be operating well below its potential output. While running the example turbo cam would work well even with the most in-efficient of the header systems out there.
Typically a overlap spread of -8 degrees to +2 is a safe bet. Of course this will differ with whatever combination header, turbo and exhaust is used, so those #'s could be higher or lower.




Lift:

How much lift should I get in my cam? Well that will depend on your heads' flow characteristics. To choose the correct turbo camshaft, you really need to know how your cylinder heads flow. Reason is if your cylinder head flows X amount of air at X amount of lift, choosing a cam that has a lift much greater then that will gain you nothing except extra heat and premature wear of the valve spring. Airflow through a head reaches a peak as the valve is opened, then starts to drop off as the valve is lifted beyond that peak. Most of this of this will hold true to definition, but with a forced induction motor, valve lift is not as critical since the incoming air is pressurized.


A good rule of thumb is to select a cam that will lift the valve 20-25% past its peak flow point.


So be the definition above if your head flows best at 0.500" of lift, use a cam that will lift the valve between 0.600" and 0.625". The reasoning behind this is, if you lift the valve only to its peak flow point, then the valve only flows best when it's wide open. The cycle is brief and would only happen once per stroke. So to benefit from you peak flow the most, you want to lift the valve past its peak. That way the valve will pass its peak flow twice in the cycle. The result is more flow during the opening and closing event of the valve. You do not want to raise the valve much past the peak flow though, or you lose total flow by going too high.
Calculating the best lift:

0.500 X 1.20 = 0.600

0.500 X 1.25 = .0625


So is this a good rule of thum?

why isnt C/L in the above post ?

I think it seems to make sense yes. I think most of the ideas behind these theories are based on looking at the pressures in the intake and exhaust tracts and trying to pick cam timing events that reduce the effects of the negatives. In other words, reducing overlap, shortening the exhaust event etc.

I have a custom ground solid flat tappet camshaft from Camotion i'll have to post.

yea if you can post the spec on it that would be great and are you selling it? i know you where doing the d3 heads rightthat cam just miye work for me.

Yup it's for sale and I am using D3's. I sent him all the info and he said that this camshaft should idle smoother than stock and produce enough exhaust pressure to run 9's in the 1/4.

I'll post it this evening and maybe take a picture or two. I don't think it has ever been out of the box.

cool cool thank you

I have the cam card scanned in andwould like to email it to you.

pm sent

Email sent! LOL

Peak flow @ .800 lift typical BBF deal. .800 x 1.125 = 1.00 lift Not typical. I think as BBF guys go, lift is set as a reliability concern to a point. One exception is the SCJ or Kasse head which peaks at .600 generally , but we all in roller applications tend to still run in the .700-.800 range. I guess that 20 -25 % deal was for mild street cams.

I would think that a good balance of intake and exhaust pressure would allow you to have a small amount of overlap to purge the chamber of any residual exhaust gasses (clean intake charge) . Also on a all out race turbo deal, exhaust valve opening @ 65-75 degrees close to peak piston speed would be where you wanted your exhaust valve to open. This would really thump the turbine and help spool. This can be gotten by juggling cam specs on intake and exhaust lobes and separation.

Hey Blake here is the cam card what do you think.

I think it will work fine............ It will be mild, should build good power everywhere.

cool deal thank you.Yea this motor is a low dollar motor if it hit the 900hp ill jump up and down with joy:)

so im looking at springs 924-16,930-16 what do you guys think i went to comp and picked a cam that was a little bigger and got the spring numbers what do you guys think? Max 20psi boost

Wow, 20 psi!! Should be a ton of fun!! The E85 should allow the big boost just fine.

By low budget, including everything you already have, what is your estimated cost of the build?

Will you be using a set of your prototype headers?

Bill

yea they will be turbo headers that i will build if they pass the test
$2000.00 crank rods pistons
$250.00 intake
$100.00 card
$150.00 QF e85 blocks
$1200.00 turbos
$500.00 heads
$1200.00 fuel system
$800.00 trans
$3500.00 chassis and suspension
$1000.00 MIsc

so full car build for $10,700.00 we are trying